1. Field of the Invention
Cholesteric liquid crystal materials cause incident radiant energy to be spectrally scattered and the spectrum is distinctive to particular environmental conditions. Cholesteric liquid crystal materials exhibit the radiant energy-scattering or light-scattering effect as a function of temperature and as a function of the composition which includes the liquid crystals.
This invention relates to analysis of the light scattering properties of compositions which contain cholesteric liquid crystal materials. It more particularly pertains to a device for causing and observing such light scattering under controlled conditions.
This invention pertains to a device for exposing a light scattering composition to incident light and to a process for exhibiting the scattered light spectrum on a viewing screen. The invention more particularly pertains to such a device wherein the spectrum scattered light is a broad spectral display.
2. Description of the Prior Art
Iridescent reflection of incident white light from cholesteric liquid crystal materials is well known. U.S. Pat. No. 3,114,836 issued Dec. 17, 1963 discloses display devices which utilize cholesteric liquid crystal materials to present thermal patterns or outlines of thermal bodies. The device therein includes a film coated by liquid crystal material and positioned such that an observer normal to the film can watch the liquid crystal material undergo iridescent color change over a period of temperature change in the film.
U.S. Pat. No. 3,441,513 issued Apr. 29, 1969 discloses spectral scattering of white light incident on films of a variety of cholesteric liquid crystal compositions.
Several technical journal articles have discussed temperature sensitive light scattering of liquid crystal materials and devices for observing such light scattering. Examples of pertinent articles are: Fergason, J. L., Molecular Crystals, Volume 1, pp 293-307 (1966); Fergason, J. L., Goldberg, N. N., and Nadalin, R. J., Molecular Crystals, Volume 1, pp 309-323 (1966); and Adams, J., Haas, W., and Wysocki, J., Molecular Crystals and Liquid Crystals, Volume 8, pp 9-18 (1969). The light scattering disclosed therein is not revealed, or understood, to be a spectral reflection from a film at a single temperature.